Damage,Collapse And Protection Of RC Frame Structure Under The Synergistic Effects Of Blast And Fragments

With the improvement of economic level,China’s building industry ushers in a great development,and the theoretical system of reinforced concrete structure is becoming more and more perfect.In this paper,the finite element analysis software ANSYS / LS-DYNA is used to simulate the damage characteristics and rules of cast-in-place reinforced concrete frame structure and prestressed prefabricated reinforced concrete frame structure under the action of the blast wave and prefabricated fragments.Based on the finite element model,the main achievements are as follows:(1)A finite element model consisting of cast-in-situ reinforced concrete frame structure and prestressed prefabricated reinforced concrete frame structure,explosives,air,fragments and rigid ground was established.Through the numerical simulation of dynamic response of frame structure,fragment velocity driven by explosives and penetration depth of fragments into concrete under explosive load,the material constitutive model,research method,contact type and control parameters selected in this paper are verified rationality.(2)The damage and continuous collapse of frame structure under the action of shock wave alone,shock wave and fragment are analyzed.The results show that penetration and perforation effect of fragments can weaken the ant-explosion ability of reinforced concrete.In terms of failure mode,when blast acting alone,the back blasting surface is the first to be damaged,and gradually fails with the increase of lateral displacement.The front blasting surface is the first to be damaged under the synergistic effects of blast and fragments,showing the characteristics of fragment penetration damage.(3)With the increase of fragments layers,the damage of the structure increases,the collapse rate increases,and the resistance to continuous collapse weakens.Under the external explosion condition,the number of fragments increases,the damage of the structure is greatly affected,and the collapse rate is obviously accelerated;while under the internal explosion condition,the increase of the number of fragments has limited effect on the damage degree of the structure,and the collapse rate is less accelerated.(4)The protective measure of spraying polyurea elastomer outside the column have certain anti-explosion effect.The anti-composite performance of the structure will be improved by adopting the union measures of high-strength steel wire mesh and polyurea elastomer.When strengthening the existing frame structure,the method of attaching steel plates along the beam can be used to improve the anti-collapse ability of the structure.The longitudinal reinforcement ratio can be added in a certain range of beam-column joints to strengthen the connection capacity of beam-column joints and improve the anti-collapse ability in the anti-collapse design.(5)The anti-collapse ability of the prefabricated structure is weaker than that of the cast-in-place structure.The prestressing tendon improves the anti-collapse ability of the prefabricated structure.The collapse rate of the structure can be effectively delayed when improves the concrete strength of prefabricated components and cast-in-place parts at the same time.The length of precast beam extending into the core area is longer,and the collapse rate of the structure is slower.When the total mass of fragments remains unchanged,the size of fragments increases and the damage degree of the structure decreases.When the proportion distance of explosives remains unchanged,the damage degree of structure increases with the increase of explosive amount and distance under the action of shock wave alone.